<?php
/*
 public boolean isSameTree(TreeNode p, TreeNode q) {
    if (p == q) {
        return true;
    }

    if (p == null || q == null) {
        return false;
    }

    return p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
}
*/